1. Field of the Invention
The present invention relates broadly to aluminum hydroxychloride compositions characterized by the presence of both SO.sub.4.sup.-2 anions and anions of selected organic acids. The present invention also relates to the utility of such compounds in the treatment of soft water.
2. Description of the Prior Art
Treatment of water and aqueous effluent by various aluminum salts in conventional and has long been based on the ability of such compositions as aluminum sulfate and aluminum hydroxychlorides to effect coagulation and flocculation of impurities therein. The latter of these compositions is currently enjoying an increasingly more important position in the treatment of water and aqueous effluent due to an enhanced capacity for such coagulating and flocculating of impurities and has, thus, received vast commercial attention.
Moreover, respecting these aluminum hydroxychlorides, it is known that the addition of certain anions to the basic composition provides a synergic effect in the ability to coagulate and flocculate impurities. This is particularly true of the SO.sub.4.sup.-2 anion, while it has been also suggested that the anions of phosphoric and chromic acids as well as various carboxylic acids such as citric acid, oxalic acid and various sulfonic acids may also be employed to these ends.
Notwithstanding the general efficacy of such compounds and compositions, it has been determined by applicants that the results are highly unpredictable depending upon such considerations as the anions involved and the solution to be treated. Thus, it has been observed that, although the addition of SO.sub.4.sup.-2 anions to aluminum hydroxychlorides indeed increases their effectiveness in a majority of applications, the same does not apply to the addition, even in large quantities, of most of the other anions enumerated above. More particularly, in the special and more difficult case of treating soft water, it has been determined that none of the various anions give satisfactory results, while, surprisingly, the SO.sub.4.sup.-2 anion is totally ineffective.
Accordingly, the need exists to provide effective coagulating and flocculating agents, particularly based upon the aluminum hydroxychloride compounds, for the treatment of soft water.